Our goal is to develop a standard procedure to measure the sulfur-centered radicals in carbonaceous materials used for in-vivo oxygen sensing. Having a standard technique would be useful for quantitative analysis of sulfur radical content in different types of carbonaceous and other materials. We are trying to develop a routine method to prepare samples for measuring EPR (94 GHz) of these samples in similar conditions, mostly under nitrogen environment. High-frequency EPR is susceptible to sulfur radical content; a standard technique would enable us to quantify the sulfur radical content in different specimens prepared/treated under different conditions.